added tests for issue #142

[atuttle]

It does appear that the change object can be modified when multiple are applied if one is an object.

  81 passing (94ms)
  1 failing

  1) deep-diff
       regression tests for issue #142
         should not modify the change object:

      Error: expected [ 'bar' ] to sort of equal []
      + expected - actual

      -[
      -  "bar"
      -]
      +[]

      at Assertion.assert (node_modules/expect.js/index.js:96:13)
      at Assertion.eql (node_modules/expect.js/index.js:230:10)
      at Context.<anonymous> (test/tests.js:595:45)